engine problems for a 1988 90hp mariner

[Riecus]

Okay I ordered the carb kit and it came in today. I pulled on of the carbs off and it is clean enough to eat off of yet the first 4 spark plugs are black and they are brand new. I only ran the boat once on them. The 5th and 6th plugs are clean. What else could be causing the problem? The boat will not idle long and when u put it in gear it dies. I just can't figure out why 4 of the 6 plugs are black if it is not the carb.

 

[gregpro50]

Re: engine problems for a 1988 90hp mariner

So did you rebuild the carbs or not? Many times the small orifaces get plugged up with junk while the rest of the inside looks clean. Is the spark good on those 4 cyls that are fouling?

 

[Riecus]

Re: engine problems for a 1988 90hp mariner

No i did not rebuild the carbs. I figured that if the inside was not gunked then it would not cause that much gunk to build up on the plugs. that is a lot of gunk for just a small ore face to be clogged. When you pull the first 4 plugs there is a bit of oil on the threads an inside looks pretty black. any thoughts on that

 

[j_martin]

Re: engine problems for a 1988 90hp mariner

Have you checked the obvious items? Fuel pump with a leaking diaphragm, (there would be fuel in the pulse line where it shouldn't be) and a leaking enricher valve. (always partly choked.)

Is there good fire on the fouling plugs. The question needs to be answered to decide what else to do?

By the way, a clogged idle air passage would flood out that cylinder at idle. Unlikely to have 4, though.

hope it helps
John

 

[j_martin]

Re: engine problems for a 1988 90hp mariner

Have you checked the obvious items? Fuel pump with a leaking diaphragm, (there would be fuel in the pulse line where it shouldn't be) and a leaking enricher valve. (always partly choked.) You can check that out by pinching off the enricher line with a hemostat after it's started.

Is there good fire on the fouling plugs. The question needs to be answered to decide what else to do?

By the way, a clogged idle air passage would flood out that cylinder at idle. Unlikely to have 4, though.

hope it helps
John